本文關鍵詞：煙氣中NO_x的液相氧化吸收及硝態(tài)氮的去除研究　出處：《北京化工大學》2015年碩士論文　論文類型：學位論文

  更多相關文章： 氯酸鹽氧化NO_x Na_2S溶液吸收NO_x NO_2~-還原

【摘要】：本文利用氧化—還原法脫硝技術,實現氣相中NOx的去除,并且將被吸收進入液相的NOx利用還原劑將其還原為N2,實現NOx的無害化處理。本文首先考察了NaClO、NaClO2和ClO2等三種氯酸鹽在鼓泡反應器中對NO的氧化性能,考察了氧化劑在不同氧化劑濃度、溫度、pH值等條件下對NO的氧化效率；然后研究了以Na2S作為吸收劑,其溶液的濃度、溫度、pH值以及NO2濃度等影響因素對N02的吸收特性,并且對該吸收反應的動力學進行了分析；最后本文對脫硝液中的N02-的處理進行了研究,采用Na2SO3還原NO2-為N2,考察了該反應在不同pH值、溫度、SO32-/NO2比等對N02-去除效率的影響,同時,對尿素和銨鹽法去除N02-進行研究比較。主要結論如下：實驗結果表明各氧化劑在最優(yōu)條件下,NaClO,和ClO2溶液對NO的氧化效率都可達到100%,NaClO對NO的氧化效率為50～60%左右,而且氣相ClO2對NO的氧化效率也很高。NaClO3/NaClO和NaClO2/NaClO混合液均較單獨氧化劑氧化效率強,且較經濟。NaClO2/NaClO昆合液在酸性條件下產生C102,濃度比為2.5時產生的ClO2濃度最高,ClO2與混合液協同氧化使氧化效率最高。三種氧化劑都存在逃逸現象,會與后續(xù)還原劑發(fā)生反應,與吸收NO2產生競爭,消耗還原劑。三種氯酸鹽反應后的產物主要以Cl-形式存在,氧化后的NO一部分轉化為N02,一部分被液相吸收,轉化為NO2-和NO3-,液相ClO2由于其氧化性強,將液相中被吸收的氮最終以N03-形式存在。在鼓泡反應器內研究了Na2S溶液對N02的吸收特性,研究結果表明,Na2S溶液濃度從0.30 mmol/L增加到15.8 mmol/L, NO2吸收效率和吸收速率增加明顯,而且隨著NO：濃度提高,NO2吸收效率增大：當Na2S濃度超過15.8 mmol/L, NO2吸收速率增加緩慢,Na2S濃度增加對吸收NO2的強化作用不再明顯,同時增加NO2濃度對吸收效率影響不大,說明Na2S吸收N02的過程逐漸轉為氣相傳質控制。氣相中的02使吸收反應加速,但同時也額外消耗吸收劑。在Na2S溶液中加入NaOH、濃度達0.1%時,可強化NO2的吸收。NOx中NO含量增加會導致NOx吸收率下降；即使在有NaOH的條件下,也未觀察到NOx氧化度為0.5時NO/NO2的協同吸收效應。反應為吸熱反應,升高溫度,吸收速率增大。增大氣體流量,NO：的吸收速率也增加。Na2SO3/Na2S混合液隨著Na2SO3農度增大,NO：吸收效率增大,混合液濃度增加到一定程度,吸收效率基本穩(wěn)定在90%左右。被吸收NO：的一部分被還原為N2,另一部分被還原為NO2-。Na2S溶液吸收NO2的反應為關于Na2S濃度一級,NO2濃度一級的擬二級反應。Na2SO3容液還原NO2-的實驗研究表明,在SO32-/NO2濃度比為3：2,溶液pH值5,溫度為40℃,NO2-的去除率可達99%。與尿素和銨鹽法相比,不會產生二次污染,反應條件容易控制。而且,可與煙氣Na2SO3脫硝法聯合,實現NOx的完全無害化處理。
[Abstract]:In this paper, the removal of NOx in gas phase is realized by oxidation-reduction method, and the NOx which is absorbed into liquid phase is reduced to N2 by reducing agent. In this paper, the oxidation performance of three chlorates, NaClO _ 2 and ClO2, to no in bubbling reactor was investigated. The oxidation efficiency of oxidizer to no was investigated under the conditions of different oxidant concentration, temperature and pH value. Then the absorption characteristics of N02 with Na2S as absorbent, solution concentration, pH value and NO2 concentration were studied, and the kinetics of the absorption reaction was analyzed. Finally, the treatment of N02- in denitrification solution was studied. The reduction of NO2- to N2- by Na2SO3 was investigated at different pH values and temperatures. The effect of SO32-/NO2 ratio on the removal efficiency of N02- at the same time. The removal of N02- by urea and ammonium salt is studied and compared. The main conclusions are as follows: the experimental results show that each oxidant is NaClO under the optimum conditions. The oxidation efficiency of no in both ClO2 solution and NaClO solution is about 50 ~ 60%. The oxidation efficiency of gaseous ClO2 to no is also very high. The oxidation efficiency of NaClO _ 3 / NaClO / NaClO2/NaClO mixture is higher than that of single oxidant. More economical. NaClO _ 2 / NaClO _ Kun solution produced C _ (102) under acidic conditions, and the highest concentration of ClO2 was obtained when the concentration ratio was 2.5. The synergistic oxidation of ClO2 and mixed solution leads to the highest oxidation efficiency. All three oxidants escape and react with the subsequent reducing agent and compete with the absorption of NO2. The products of the three chlorate reactions mainly exist in the form of Cl-. The oxidized no is partly converted to N02and partly absorbed by liquid phase and converted to NO2- and NO3-. Due to its strong oxidization, the nitrogen absorbed in liquid phase is finally in the form of N03-. The absorption characteristics of Na2S solution to N02 in bubbling reactor are studied. When the concentration of Na2S solution increased from 0. 30 mmol/L to 15. 8 mmol / L, the absorption efficiency and absorption rate of NO2 increased significantly, and with the increase of no: concentration. The absorption efficiency of NO2 increased: when the concentration of Na2S exceeded 15.8 mmol / L, the increase of NO2 absorption rate was slow. The enhancement effect of Na _ 2S concentration on the absorption of NO2 was not obvious. At the same time, increasing the concentration of NO2 has little effect on the absorption efficiency, which indicates that the absorption of N02 by Na2S is gradually controlled by gas phase mass transfer, and the absorption reaction is accelerated by O2 in gas phase. At the same time, the absorbent was also consumed. When NaOH was added to Na2S solution and the concentration reached 0.1, the increase of no content in NO2 could lead to the decrease of NOx absorptivity. Even under the condition of NaOH, the synergistic absorption effect of NO/NO2 was not observed when the oxidation degree of NOx was 0.5. The reaction was endothermic reaction, increasing temperature, increasing absorption rate and increasing gas flow rate. No: absorption rate also increased. Na2SO3 / Na2S mixture increased with the increase of Na2SO3 degree: absorption efficiency increased, and the concentration of mixed solution increased to a certain extent. The absorption efficiency is about 90%. Part of the absorbed no is reduced to N2. The other part was reduced to NO2-.Na2S solution to absorb NO2 in the first order of Na2S concentration. The experimental study of the pseudo-second-order reaction. Na2SO3 volumetric reduction of no ~-~-in the first order of NO2 concentration shows that when the concentration ratio of SO32-/NO2 is 3: 2, the pH value of the solution is 5, and the temperature is 40 鈩，

本文編號：1364848